Commander Tucker and Lt. Reed have been on a mission to test the targeting scanners on Shuttlepod 1, requiring them to fly the craft at least 20,000 kilometers from Enterprise. During their trials they experienced an unusual jolt that disabled their sensor array and com system, forcing them to return early to the asteroid field where Enterprise has been engaged in a mapping project. Upon arriving at the rendezvous point, the two men are shocked to find a field of debris on an asteroid's surface, including a hull fragment that is unmistakably a piece of Enterprise.
Meanwhile Enterprise is actually transporting a group of Tesnians back to their homeworld after their ship was mysteriously destroyed in the asteroid field. The Tesnian ship was attempting to dock with Enterprise when it went out of control, tearing off the Enterprise launch bay door and crashing into the asteroid. Fortunately the crew escaped, and Captain Archer expects to reach Tesnia in enough time to get back to the rendezvous point before Tucker and Reed return. T'Pol hypothesizes that the damage was caused by a micro-singularity, which Archer dismisses as a Vulcan myth.
Under the belief that the wreckage is the remains of Enterprise, and with sensor and com systems off-line, Tucker and Reed can only assume the worst, that their crewmates are dead. With only 10 days of air, Tucker decides to set course for Echo III, the nearest subspace amplifier, grimly accepting the fact that at the shuttlepod's sublight speed they will never get a distress beacon out in time to be rescued, but at least Starfleet will know what happened. En route Tucker tries in vain to restore the pod's systems, while Reed spends hours logging letters to family and old girlfriends saying goodbye and tying up loose ends in his life. The two men get on each other's nerves as Tucker's hope that they will somehow be found alive clashes with Reed's more "realistic" pessimism. With nine days of oxygen left, Tucker insists they get some rest. Reed finds himself in Sickbay, with T'Pol seductively congratulating him for his heroics, but unfortunately it's just a dream, which he's torn from as he's awakened by the noise of the receiver Tucker just repaired. Suddenly the pod jolts—the same kind of jolt that knocked out their sensor array earlier—and air starts escaping into space. Using nitrogen gas to find the tiny leaks and leftover mashed potatoes to temporarily seal them, they realize whatever hit them went clear through the pod. And on its way out of the cabin, it was kind enough to rupture one of the oxygen cylinders, leaving them with less than two days of air.
Using valve sealant to permanently fix the cabin leaks, they wonder how such a tiny object could penetrate the skin of the pod that's designed to withstand meteors five times that size. Then Tucker realizes they can buy another half day of air by diverting power from the temperature regulator to the atmosphere recyclers, so the men opt to endure freezing cold. On Enterprise, T'Pol presents evidence to Archer that the Tesnian ship indeed was struck by a micro-singularity, because three of these "tiny black holes" also collided with the polarized Enterprise hull, but dissipated on impact. Though skeptical of her theory, Archer decides it would be dangerous for the shuttlepod to enter the asteroid field again, so he orders T'Pol to hail Tucker and Reed to set a new rendezvous point. Meanwhile, under the stress of extreme cold, the two stranded officers argue over their respective attitudes toward their plight, Tucker accusing Reed of being a "grim reaper" and Reed accusing him of "treacly optimism." But they do come together in a toast for the brave men and women of the Starship Enterprise. As they huddle together under a blanket with a bottle of Kentucky bourbon, they hear a crackling voice on the receiver — it's Hoshi, giving them new rendezvous coordinates. Enterprise is okay! The bad news is, they're still two days away and the pod only has only a day's worth of air, and with the transmitter still out, there's no way to tell them to get there sooner.
Desperately trying to figure out what to do, such as finding ways to extend their air supply, Reed and Tucker realize the math is just not on their side. So their only course of action is to attract the starship's attention to get them to go to high warp. At Reed's suggestion, Tucker agrees to jettison the pod's impulse engine rigged to self-destruct, causing an explosion that they hope will show up on T'Pol's viewer. But doing so leaves them adrift, and they go hours without knowing if their message got through. Finishing off the bourbon with ten hours of air left for two people, Tucker decides to double the odds of one of them surviving, so he climbs into the airlock to seal himself off, but Reed tries to argue him down and even points a phase-pistol at him — he'd rather Enterprise find both of them dead than one, but he's become hopeful things will work out. Tucker relents, and the two men sit side by side in the cold, waiting and shivering.
Reed opens his eyes to find himself in Sickbay, with Archer, Phlox and T'Pol informing him he's suffering from hypothermia, but was rescued with only two or three hours of air left. Reed wonders if T'Pol has something to say to him about "heroics," but she doesn't — this isn't a dream. He turns to the still-unconscious Tucker and acknowledges his fellow officer as his friend.